Burst Your Bubble

To ruin someone’s happy moment or mood, usually by telling them disappointing news or information.When someone is really excited or confident about something, you burst their bubble when you say something to disappoint them.
毁掉一个人的好心情，通常是告诉他们失望的消息。当一个人处于非常兴奋或自信的状态时，你说了些扫兴的话burst their bubble。

I hate to be the one to burst your bubble, but your school's team didn't win last night.
我讨厌做那个煞风景的人，但是你学校的队伍昨晚没赢。